Energy monitoring, in its known and common usage, as a unique sensing point for an entire unit, such as a Smart Meter, has many limitations. For example, it is very difficult to track the behavior of one piece of equipment or appliance over time, because only the aggregate energy consumption is recorded, making it difficult to isolate that equipment. Additionally, appliance manufacturers have very little data concerning the way with which the users employ these appliances. This information, if available, would lead to more user-friendly and more energy efficient appliances. With the advent of the Smart Grid, real-time energy consumption data from specific appliances becomes necessary to better distribute the limited resources generated by the utility companies.
There have been some attempts in the prior art at providing a plug-level energy monitoring solution. However, most of the products on the market today use some sort of resistive sensor, which breaks the current path from the cord to the wall outlet. Moreover, this method of energy monitoring dissipates power and makes the sensor bulky and expensive, rendering it unattractive for the users. Additionally, the energy consumption of the sensor itself grows with the consumption of the equipment or appliance. Though this may seem insignificant in the context of one or two instruments, but when scaling this technology to every outlet in every residence or office it presents a major obstacle for adoption.
The present invention is an inexpensive and scalable solution for the plug-level energy monitoring problem. With many integration points, it is a very slim device that allows continuously measuring the energy consumption of the equipment or appliance, without breaking the current path to the wall. Additional benefits include (a) no additional series resistance to be inserted in the circuit for current sensing, which can save a significant amount of power for certain loads; and (b) the advantage of incorporating the sensor into PCB allows the use of standard manufacturing process, reducing component count and costs. Furthermore, in certain embodiments, the distance between a conductor and sensor can be fixed by PCB design, thereby mitigating concerns related to calibration for the distance between conductor and sensor.
Additionally, the present invention advances the design and operation of a Ground fault circuit interrupter (GFCI). GFCI outlets are typically used in kitchens and bathrooms due to the presence of water, which makes the risk of electrocution higher. A GFCI outlet is able to sense if electric current is flowing through an unintended path, and then break the circuit to stop the flow of electric current and disable the outlet. GFCI outlets typically employ a current transformer that encompasses both the hot and neutral wires. The signal from this current transformer is connected to a printed circuit board (PCB) with additional electronics. During typical operation, the electrical current flowing in the hot and neutral wires are of the same magnitude, and in the opposite direction. Thus, the voltage observed across the current transformer terminals is typically zero. However, if there is an alternate current path, e.g. through a person, the currents through the hot and neutral wires will not be the same. In this case, the current transformer voltage will be non-zero, providing a signal to an electrical or mechanical switch/relay to break the circuit. The present invention, however, permits the integration of the GFCI into the PCB of the invention yielding improvements of the current state of the art.